Melt remaining ½ cup of butter and unsweetened chocolate in a saucepan over low heat. Combine the eggs and confectioner’s sugar in a bowl and add the melted chocolate mixture, beating until thickened. Pour chocolate mixture over the cooled crust. Freeze until firm. Spread the ice cream into a layer over the frozen chocolate mixture and frost with the Cool Whip. Sprinkle shredded coconut over the top, if desired. Freeze until firm.